ReactiveX/Rx.rb — pull request #31 by jca02266 (2014-12-20 05:23:55+00:00)
Title: Implement interval

Add Observable.interval for below example

```ruby
require 'rx'

source = RX::Observable
.interval(0.5) # ms
.time_interval()
.take(3)

subscription = source.subscribe(
lambda {|x|
puts 'Next: ' + x.to_s
},
lambda {|err|
puts 'Error: ' + err
},
lambda {
puts 'Completed'
})

sleep 3
# => Next: (0)@(0.5120988)
# => Next: (1)@(0.5000763)
# => Next: (2)@(0.515575)
# => Completed
```